Tetrapotassium pyrophosphate

Dissociation constant

Administrative data

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
See read-across justification report under Section 13 ‘Assessment Reports’.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
In accordance with REACH Annex XI, Section 1.5, of Regulation (EC) No. 1907/2006 (REACH) the standard testing regime may be adapted in cases where a grouping or read-across approach has been applied.

The similarities may be based on:
(1) a common functional group
(2) the common precursors and/or the likelihood of common breakdown products via physical or biological processes, which result in structurally similar chemicals; or
(3) a constant pattern in the changing of the potency of the properties across the category


Read-across is justified on the basis that pyrophosphoric acid is the parent acid for all inorganic pyrophosphates.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See read-across justification report under Section 13 ‘Assessment Reports’.

3. ANALOGUE APPROACH JUSTIFICATION
See read-across justification report under Section 13 ‘Assessment Reports’.

4. DATA MATRIX
See read-across justification report under Section 13 ‘Assessment Reports’.

Cross-reference

Reason / purpose for cross-reference:

read-across: supporting information

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Report date:

2009

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

No experimental determination of the dissociation constants in water was performed for the test materials as it was anticipated that on performance of the test procedures, as detailed in Method 112 of the OECD Guidelines for Testing of Chemicals, 12 May 1981, that the resulting dissociation constants determined would be that of the parent anions only, for which literature values are available. For example, it is anticipated that different types of orthophosphate will demonstrate significantly different pH values in water due to increasing numbers of protons being substituted with the particular cation on titration with acid or base as appropriate, the actual dissociation constants determined for each compound would be common, i.e. that of the triprotic acid anion. Titrations would also be expected to be similar irrespective of the counter ion.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Pyrophosphoric acid

EC Number:

219-574-0

EC Name:

Pyrophosphoric acid

Cas Number:

2466-09-3

Molecular formula:

H4O7P2

IUPAC Name:

diphosphoric acid

Details on test material:

- Name of test material (as cited in study report): pyrophosphoric acid

Results and discussion

Dissociating properties:

yes

Dissociation constant

Dissociation constant 1

No.:

#1

pKa:

0.9

Temp.:

25 °C

Dissociation constant 2

No.:

#2

pKa:

2.31

Temp.:

25 °C

Dissociation constant 3

No.:

#3

pKa:

6.69

Temp.:

25 °C

Dissociation constant 4

No.:

#4

pKa:

9.42

Temp.:

25 °C